This relates to the formation of different types of transistors on the same integrated circuit wafer.
In the course of manufacturing microelectronic memories, such as flash memories, additional circuitry may also be needed to control the flash memory array. The flash memory array may include a matrix of flash memory cells operated under control of control circuits in what may be called the periphery or area outside the array.
These peripheral circuits may include different types of transistors, including relatively lower voltage, higher performance transistors and relatively higher voltage transistors. The characteristics of these transistors differ from each other, as well as from the characteristics of the memory cells, and, thus, advantageously, the processes used to manufacture them are different as well, even where all of these devices are formed on the same wafer.